Terra seems really polarizing, yeah.
Spoiler for Terra:
Basically every single thing that happens in Terra is predetermined. This might be obvious, but that was the whole point of all the non-choices.
It's a subtle and very meta take on the nature of true routes in visual novels. Really beautiful, in my opinion.
As for why Kotarou doesn't wait to get the Occult Club together again or whatever, well... the whole point of Kotarou's development in Terra is that he can only reach his desired ending by throwing away everything that matters to him. That would include the Occult Club.
Moon was a way of saying goodbye to them anyway, so if it makes you feel better you can regard it as the game's "grand finale" and Terra as a sequel/spinoff of sorts.